Estimating Catchment Area Population Indicators Using Network Analysis

Abstract

This paper proposes an approach to estimating catchment area population indicators (CAPIs) using geographic information system (GIS)-based network analysis. Specifically, it considers how 'GeoDirectory', a geodatabase containing the spatial coordinates of every building in the Republic of Ireland, can be used in conjunction with estimated service areas to calculate the number of residential buildings within a catchment area. The count of residences within the catchment then acts as an indicator or proxy for its population and can be useful when the catchment area does not match closely any combination of geographical or administrative areas for which data exists. Two small-scale recreation forest sites in County Galway are considered by way of illustration: Barna Wood and Renville Forest Park. CAPIs are estimated for the two sites using distance-based service areas as well as isochrone surfaces, and comparisons are made to estimates based on measures of Euclidean distance. The analysis suggests that network-based service areas are useful for deriving catchment population indicators, that road density has a significant impact on catchment area size and that caution must be exercised with respect to travel speed assumptions when estimating isochrone surfaces.